Gas turbines generally include a rotor with a number of rows of rotating rotor blades which are fixed to a rotor shaft and rows of stationary vanes between the rows of rotor blades which are fixed to the casing of the gas turbine. When a hot and pressurized working fluid flows through the rows of vanes and blades it transfers momentum to the rotor blades and, thus, imparts a rotary motion to the rotor while expanding and cooling. The vanes are used to control the flow of the working medium so as to optimize momentum transfer to the rotor blades.
A typical gas turbine rotor blade comprises a root portion by which it is fixed to the rotor shaft, an aerodynamically formed airfoil portion the design of which allows a transfer of momentum when the hot and pressurized working fluid flows along the airfoil section. It further comprises a platform that is located between the root portion and the airfoil portion. The surface of the platform which shows towards the airfoil portion forms a wall section of the flow path for the hot and pressurized working medium.
Since the working medium is hot the turbine blades of a row of blades are installed such to the rotor shaft that gaps remain between neighboring platforms so that an expansion of the gas turbine rotor blade due to the heat of the working medium is not hindered. Moreover, in order to actively cool the turbine blade a cooling fluid, typically pressurized air from the compressor, is led along the root side of the platform and sometimes also through the interior of the airfoil section. In older designs open cooling loops have been used in which the pressurized cooling air is released into the flow path of the working medium after passing the turbine blade. However, high efficiency gas turbine engines require closed cooling loops, in which the cooling air is not released to the flow path of the working medium but returned to the compressor after recooling it. Such closed loop cooling systems rely on sealing the gap between neighboring rotor blades.
Rotor blades with sealing strips or sealing pins between neighboring rotor blades are disclosed in DE10346384A1, US2009/169369A1, US2010/0284800A1, U.S. Pat. No. 6,273,683 B1, US
U.S. Pat. No. 6,561,764 B1, US 2010/0129226 A1, and EP 2 201 271 B1. Typically, such sealing strips or sealing pins are held in place by grooves located in side faces of the platforms. Since also the sealing strips expand when exposed to the hot working medium the dimensions of the grooves are typically a bit larger than the length and the thickness of the seal strips or seal pins.